Sh2-171 and Sh2-272
SH2-271 and SH2-272 are two emission nebula, part of a much larger mostly invisible to visibly light molecular cloud in northern Orion just east of his club. The naked eye B9 blue giant star, 73 Orionis, is in the upper left of my image. It created havoc in processing this image as it scattered a blue gradient everywhere. I have severely retarded this star so it appears many times fainter than it really is at magnitude 5.4.
Many catalogs, including the data base in my The Sky 6 program say the larger nebula, SH2-271, a planetary nebula calling it PK 197-02.1. It's in other planetary nebulae catalogs as well according to SIMBAD. The nebulae are excited by the two stars seen in their centers, an 09V and B1V stars. For some reason SIMBAD locates SH2-271 4.5 minutes of arc east of its location and SH2-272 0.4 minutes west of its location. I don't know why the errors. The Sky makes the same error for SH2-271. SIMBAD also places a star cluster midway between the two nebulae's actual positions. Most of these stars are seen in IR rather than visual light as they are buried deep in the molecular cloud, two small parts of which make up the two visual nebulae.
While sources vary for a distance to these nebulae most say it is in the Perseus arm and give a distance of 15,600 light-years. Some include an error bar of 4,000 light-years. Distances for objects like this can be hard to determine. Assuming the 15,600 light-year distance the two nebulae span a distance of about 19 light-years.
Conditions were lousy when this was taken. So bad I threw out all the luminance data as too blurry to use due to fogging from high clouds and 73 Orionis. Instead I used the two red images as less blasted by the star plus the H alpha data to make a pseudo luminance image. The H alpha data was added 80% to the red and 20% to the blue when making the RGB image. That left a severe issue with blue and to some extent green due to 73 Orionis and high clouds scattering its light. I had to use a lot of gradient tools to restore the color balance. Still there's some glare around many stars. I need to redo this one on a night of much better transparency. I tried this one another night under slightly better conditions and moved 73 Orionis out of the field but that caused highly distorted ghostly images all over the image. These were even worse to deal with and the halos around the stars from the thin clouds just as bad. I never had weather conditions sufficient to try again.
14" LX200R, HA=4x30' RGB=2x10', STL-11000XM, Paramount ME